With some growers spending about £150/ha on herbicides to control blackgrass and still not achieving acceptable control, farmers have been told it’s time for a rethink on how they produce their crops. Adam Clarke reports.

Arable farmers fighting to control rampant blackgrass need to make radical changes to their cropping systems to bring the grassweed down to manageable levels.

Blackgrass is a hot topic at this time of year, with huge populations showing above winter wheat crops this season evidence of the scale of the problem and the need to improved control measures.

See also: High wheat costs may carry over into next season

Agrii’s head of crop science and stewardship David Langton told Farmers Weekly that some growers have now “hit a brick wall” and if they want to continue growing wheat they should consider revising the way they farm.

“There are no get out clauses and herbicides can no longer be relied upon, with some growers this year spending up to £150/ha and still getting lousy control,” he added.

Mr Langton said that it’s a useful exercise for growers to try and measure the extent of their problem, with infestations of 100 blackgrass ears/m sq penalising yield by about 1t/ha.

“Using that equation, it can put the scale of your problem into context by counting the blackgrass populations in your crop and it might be a wake up call for some,” he said.

So what are the radical changes that need to be made?

Rotation is the first part of the system to address and it is well known that spring cropping is one of the most effective control measures to reduce blackgrass.

Dow AgroScience’s Stuart Jackson said that the three-crop rule might be a useful opportunity to deploy spring cropping in the fight against blackgrass.

“Winter wheat followed by oilseed rape is not a rotation and spending £140-160/ha on loading up herbicide programmes is not sustainable.

“A grower’s historical bottom line might be better growing winter crops than spring, but incurring costs as high as that to control blackgrass can’t be kept up for long,” he added.

Clean slate

Many of the independent commercial trials investigating the best methods for controlling blackgrass point towards cultivation as the next critical area to address.

Mr Jackson advised growers to review their cultivation strategy and those that have not ploughed for many years should think about doing so this autumn,

“There will be an extremely high seed return for some this year and where min-till systems have been mixing the top 15-20cm of soil year on year, there will be seed waiting to germinate.

“Getting a couple of inches below that level and turning it over will allow crops to start with a clean slate in the autumn, but the ploughing needs to be high quality, or you could make things a whole lot worse,” said Mr Jackson.

Mr Langton explained the “big two” of rotation and cultivation would provide the biggest gains, but other factors such as delayed drilling of winter wheat, variety choice and seed rates are also useful elements of the overall strategy.

He added that those who have not yet “hit the wall” also needed to think about employing all elements in their system to avoid getting to that point.

“It may mean lower margins, but growers should be doing much more than they need to do to prevent their own problem getting worse,” said Mr Langton.

Chemicals still have a vital role to play and Bayer CropScience’s herbicide development manager Gordon Anderon-Taylor advised growers to use the most effective products and maximise the chances of them working.

“Hit the blackgrass hard and early with three or four active ingredients at pre- and peri-emergence. If you are using Atlantis use it early in the autumn when blackgrass is at the one to three leaf stage.

“Nice, even seed-beds will help the pre-ems and using the right nozzles and water rate will squeeze maximum control out of the chemistry,” said Dr Anderson-Taylor.